k7000 25" No Picture

troxel

Well-known member

Donor 7 years: 2015-2021
Joined
Mar 19, 2006
Messages
2,084
Reaction score
104
Location
Lincoln, Nebraska
Had a Neo Geo hooked up to a 25" k7000 and went play it, and nothing is showing. I opened it up and saw that the ground wire from the monitor was hanging loose. Should this hook up to the neck board? The neckboard ground is connected to the chassis. How should the grounds be connected? This was the only thing that looks out of place. I tried different combinations, but nothing changed.

The B+ is at 130 and tried turning up the focus, but I don't see the scan lines. When I turn off the monitor, I can see a flash and looks like a horizontal line, but it's too quick to be sure.

Any suggestions on what to check?

Thanks again.
 
It's connected to the chassis frame, where the ground around the tube isn't connected. I tried connecting the tube to the neckboard, but there wasn't a change.
 
Yes, monitor has neck glow, and when I turn it off, I can see a quick flash of raster.
 
Capkit last summer. Has original flyback. Monitor was working great until I turned it on today. That's why I was wondering if something was disconnected.
 
Usually it's pretty rare for things to just disconnect themselves.. unless you were messing with the inside of the game..

I'd pull the chassis and go over it.. if it's got the original fly, check for goo or hairline cracks.. I'd bet you also have quite a few weak solder joints too..
 
OK. Turned up the screen and got a horizontal line down the middle. Checked R91, and it was good. Does this lead to IC3 or IC2? I just read that D13 might be a cause of the problem. I will double check that tomorrow night.
 
Last edited:
Vertical collapse? IC3. Replace with the exact same part. Some versions of the K7000 used differen IC3's.

Horizontal collapse? Bad trace around the width coil...
 
I am about to replace IC3, and noticed that P723 looked rather toasty. Anyone know the specs on R603 and D601? I saw that this is for pincushion adjust, and would this cause a loss of vertical deflection? Should I put in new header pins on this, too?
 

Attachments

  • 100_0482.jpg
    100_0482.jpg
    97.2 KB · Views: 29
Last edited:
I am about to replace IC3, and noticed that P723 looked rather toasty. Anyone know the specs on R603 and D601? I saw that this is for pincushion adjust, and would this cause a loss of vertical deflection? Should I put in new header pins on this, too?


i am confused P723, R603 and D601they don't exist on a K7000.

but yes IC3 on a K7000 controls vertical deflection.

also check d15 and see if it is good.

Peace
Buffett
 
OK the plot thickens.

those are undocumented boards.

test the zenier out of circuit. hope it is good there are no docs on that board. and i do not know the value.
replace the resister if bad.
replace that cap.

remove the board and clean those two black header pins.

no need to replace them just hit them with a little fine grit sand papaer or some steel wool.
shine them up a Little and solder them back down.
also re-flow all the header joints on that card.

Peace
Buffett
 
Replaced IC3 and now greeted with no neck glow. B+ was 130 VDC and turned the screen up, and didn't get any picture. Checked R213 out of circuit and got 1.5 ohms. Is R213 0.68 ohms?

Also, Took of the P723 card and and check R603 and D601 out of circuit and both were bad. I just kept it off when I noticed no neck glow.

What's next? Replace R213?

And thanks for the help so far. I appreciate it!
 
i would fix the card and reinstall it.

seeing how it is not a socket'ed card and has to be soldered it probably affects the vertical circuit in a crucial way.

i would not worry about the neck resister just yet.
get the card fixed and retry.

also check the cable that feeds the neck board the power to that resister for an intermittent connection.

then if it still does not work then i would suspect the resister on the neck board.

let the chassis run and measure the output side of the resister to see if it is not letting the correct amount of current to pass. it should be around 6 volts or so.

Peace
Buffett
 
Back
Top Bottom